Pneumatic air brakes have been in use for more than 100 years and have been an extremely reliable system. In recent years electronic controls have been incorporated in the air brake system. The introduction of electronic controls increases the precision of the braking system while maintaining the strength, reliability and efficiency of pneumatic power.
These electrical or electronic control systems generally require batteries in the individual railway freight car and it is desirable to provide a generator on each car to maintain the batteries in a charged condition. For most of the Electronically Controlled Pneumatic (ECP) braking systems a small power level may be sufficient to keep the batteries charged.
One of the challenges in the development of (ECP) brake equipment for railway freight cars is to have a way to supply electrical power required by the electronics. This power supply must be reliable in typical railroad environments, easy to operate and maintain, and not interfere with the operations of the train.
Some current designs of ECP systems call for a battery system trickle charged by a power source from a front end locomotive. This method requires installation and maintenance of a cable line on each car. In addition to the connection of the brake hoses, the cables must be connected when cars are linked to form a train. In a typical railroad environment, the connectors used must be protected from damage and corrosion.
Another design that has been tested on trains is a vibration operated generator. This system eliminates the cable, but it operates only when the train is moving because it relies on vibration. When cars need to be charged before they move, a separate charging system must be used.
There is a need for an on-board electrical generator that does not require a cable link on each car and yet can keep the batteries in a charged condition even when the train is standing still.